As is shown in FIG. 1, there has been proposed a composite disk 1, known as a CDV, having information recorded thereon, and which is divided into an inner-circumferential first area (hereinafter referred to as a "CD area") 1a and an outer-circumferential second area (hereinafter referred to as a "video area") 1b. In such a CDV, for example, audio information subjected to PCM (Pulse Code Modulation) is recorded in the CD area 1a, and a video signal subjected to frequency modulation and an audio signal subjected to PCM are recorded in the video area 1b.
A video signal includes a higher frequency component in comparison with a PCM signal, and therefore it is necessary to make the rotational speed of the CDV disk 1 higher when recording a signal onto the video area 1b than when recording a signal onto the CD area 1a. Consequently, it is necessary to play the video area 1b of the CDV 1 at a rotational speed which is relatively high in comparison with that in playing the CD area 1a. For example the rotational speed of the disk 1 is about several hundred rpm in the CD area 1a. whereas the rotational speed of the disk 1 in the video area 1b is about two thousand and several hundred rpm in the innermost circumference of the video area 1b, and is about one thousand and several hundred rpm in the outermost circumference of the video area 1b.
In the case of stopping a spindle motor in a disk player which can play such a composite disk, it is possible to easily stop the spindle motor when playing the CD area, for example, by supplying a counter torque brake to the spindle motor for a certain period of time after the point of time when a stop command is given because the rotational speed of the spindle motor is low when playing the CD area. On the other hand, it is impossible to perform the time stopping control operation discussed above in connection with the CD area when playing back information recorded in the video area 1b since the rotational speed of the disk is very high.
In Japanese Published Patent Application No. 63-316682 filed by the same applicant as this application, there has been proposed an apparatus comprising a rotational frequency detecting circuit for generating a rotational frequency signal with a level corresponding to the rotational frequency of a spindle motor, a level comparator for detecting when the signal level of the rotational frequency signal becomes lower than a set reference level, a window comparator for detecting when the signal level of the rotational frequency signal falls within the range between an upper limit reference level and a lower limit reference level, with the above-mentioned set reference level as a center level, so as to perform the stop control of the spindle motor on the basis of the respective detection outputs of the level and window comparators.
FIG. 2 shows an example of the apparatus disclosed in the Japanese Publication cited above. However, as seen in FIG. 2, the resulting circuit arrangement which includes the necessary rotational frequency detecting circuit and the level and window comparators is rather complicated, and therefore is expensive to produce.